1. Technical Field
The present invention relates to an electrically-chargeable element control device, a liquid ejection device having an electrically-chargeable element, and a method for controlling an electrically-chargeable element.
2. Related Art
A control device which is for controlling charge and discharge of an electrically-chargeable element such as a piezo element or a capacitor is used in an inkjet printer (that is, a type of a liquid ejection device; hereinafter referred merely to as a printer), for example. Some of the control devices control charge and discharge by utilizing resonance between a coil and an electrically-chargeable element (see JP-A-11-320872, for example). Utilizing resonance enables driving without consuming electric power and this is useful for saving energy or for solving a problem of heat evolution which occurs when a linear amp or a resistive element is used for driving. In case of utilizing resonance between a coil and an electrically-chargeable element as mentioned above, a completion rate of charge with respect to time is determined depending on a resonance cycle. Accordingly, in the case of a printer, an amount of ink ejected is changed as the resonance cycle varies. Here, the resonance cycle varies depending on capacitance of an electrically-chargeable element. Therefore, if the number of electrically-chargeable elements to be charged and discharged, that is, the number of nozzles to eject ink, varies, an amount of ink ejected from one nozzle also varies. Accordingly, there is a need for a system to keep a resonance cycle uniform regardless of the number of nozzles to eject ink. In the above-mentioned control device, a capacitor for adjusting capacitance (a dummy capacitor) is provided in order for a resonance cycle to remain uniform.
In the above-mentioned control device, there is an advantage that a resonance cycle can remain uniform regardless of the number of electrically-chargeable elements to be charged and discharged. However, a current which flows at the time of charge and discharge also remains uniform regardless of the number of electrically-chargeable elements to be charged and discharged. More specifically, an amount of the current becomes an amount necessary to charge and discharge all electrically-chargeable elements at any time of charge and discharge. Furthermore, since capacitance of commercially available capacitors is standardized, it is necessary to use a custom-made capacitor having specific capacitance or a plurality of capacitors having different capacitance in order to obtain desired capacitance.